Devices, systems and methods for delivering one or more drugs to the cerebrospinal fluid periodically replace continuous infusion of the a solution with intermittent bolus infusion of the solution to reduce the local concentration of a drug over time at a vertebral level in the patients spinal canal relative to the drug infused continuously through the infusion section of a catheter intrathecally into a patients spinal canal at the vertebral level. Such periodic replacement of continuous infusion with intermittent bolus infusion assists in prevention formation of an inflammatory mass at the vertebral level.
